It is not known when the Nosanseong Castle was first built since it does not have any actual records. However, it has been estimated to have been constructed in the Unified Silla Period (676-935), based on the given relics that were found and collected inside the castle. Furthermore, judging from the fact that most of the relics gathered were from the Goryeo Dynasty (918-1392) and Joseon Dynasty (1392-1910), wherein it would have been probably used until those periods, while going through a repair and reconstruction process.

Located in Nosan Mountain, a main mountain in PyeongChang, Nosanseong Castle was built on Nosan Mountain, 419 meters above sea level which soars over the place where PyeongChanggang River meanders. On 3 sides, the Nosancheong Castle is surrounded by the river and the northern part of the castle is a cliff or pretty much steep. That is why it is called a natural stronghold.

The circumference of the castle is 517 meters and the height of the castle wall is around 1.3 meters or so.
The Nosanseong Castle was built over the parts ranging from the middle to the summit of the mountain whose topography is the tallest on the north and is the lowest in the south. Excluding the parts of the northern part of the castle which was not built as it was a natural stronghold, the gross length of the remaining circumference which was actually constructed with stones is approximately 517 meters. The circumference of the western southern wall is roughly 115 meters, of which, the most well-kept and remaining wall is 8.2 meters in length and 5.3 meters in height.
Judging from the patterns of the roof tile fragments, the Nosan mountain fortress is seen to have already started to be built at least in the Unified Silla Period and afterwards, to have gone through a reconstruction process several times in the Goryeo and Joseon Dynasties.
Most of the walls of the castle with a circumference of 517 meters were demolished, but the castle site is still highly valuable in that the then- Country Head, Kwon Doo-mun fought the Japanese military with his people during the Imjin War(1592-1597) and so it holds a long-held historic significance.